Pixhawk Y6 Copter looses control in Auto Mission

Good day.

We are using a Y6 copter with 15X8E and 15X10EP props.

Controller is a Pixhawk with standard 3DR GPS and 3DR radio link. Transmitter used is a Futaba T14SG and a R6303SB receiver.

Firmware version is 3.1.5. (latest)

We do measurements with the aircraft and for this mission a whole range of vertical measurements. We created a flight plan with a Auto take-off, condition yaw to face the heading to be measured, then a vertical climb to 100m, a 360° loiter turn at the top and then a decent to 5m with then land as the last waypoint.

We did for this mission 60 verticle measurements as described above. On the last flight, when reaching the 5m mark, and then switching to land as per the flight plan, the aircraft started a uncontrolled wobble after which the pilot switched to stabilize mode.

The aircraft did however not respond to the transmitter inputs as would be expected.

Eventually the pilot cut throttle and the aircraft had a light crash.

We heve been using the pixhawk controller in our aircraft with great success. This is our first actual crash incident.

Can anybody please assist in determining the cause of this incident?

I am attaching the log file. It is the last vertical flight on this log.

Thanking you in advance.


RPA Operations Coordinator

Most likely a powerplant failure.

You could try doing an autotune (no gimbal or loose mass, minimum payload). You might find yourself more in control in this situation.

Hi Jonathan

What do you mean with a possible powerplant failure?

If I look at the Roll vs Des Roll and also Pitch and Des Pitch it looks like a sort of oscilation effect.

Do you think it is possible pid gains settings too sensitive?

Is this why you suggested a autotune?

Thanks for your input!!



I really doubt it… but I suggest an autotune because it would help the copter stay stable in the event of some kind of problem. Clearly you were able to fly for quite a while beforehand without any oscillation, and then “something” happened and the copter went crazy. That “something” wasn’t any known issue with arducopter 3.1.5 (which has had something like a year of testing) or a low battery as far as I can tell, so I can only conclude that there was some sort of powerplant failure. Can’t tell you any more than that, really…

On that note, regarding the battery… I took another look and I now suspect you are running a separate battery into the PIXHAWK’s power module. Are you sure you didn’t run out of battery?

Hmm, judging by your throttle required to hover, you were probably replacing the flight battery between each arming. So you’d only really flown that battery for 4 minutes.

Hi Jonathan

Yes, you are quite right. Because of the 18V limit of the 3DR power module we are supplying the pixhawk with a seperate battery. We monitor the main batteries via the telemetry on our transmitter.

We do change the main batteries after each flight.

We did find a power module at RangeVideo that supports up to 10S batteries. Great!

We also did a autotune and the end result was almost double the previous settings. So also definately not too high gains.

At this stage still a mystery.

Thank you for your input!



I wasn’t saying your gains were too high, I was saying they were too low. I think you had a powerplant issue (ESC glitch or the like) and it didn’t have enough margin and control to keep the copter flyable.

By the way, since you have no forward-facing camera that needs the props out of view, an X8 would probably be better-suited to your task - the redundancy is more reliable.

I’ve also been meaning to try twisted arms on a Y6. Do you want to try slightly twisting your arms all in the same direction until the upper-lower motor throttle ratio is roughly zero in a hover? It should help it survive a motor failure (currently you may have critical motors that are single points of failure).

Hi Jonathan

Thank you!

I understand the gains issue better now!

Will definately look into the other points you raised!

Appreciate your input! Will keep you posted.

Kind regards